There is a solar cell in which an electrolytic solution is enclosed between electrodes. For example, there is a dye-sensitized solar cell in which an electrode in which porous bodies made of titanium oxide or the like are loaded with a sensitizing dye (also called a photosensitizing dye) and an electrolytic solution are enclosed between a pair of substrates.
In order to improve the mechanical strength of the porous body made of titanium oxide and the adhesion between porous bodies, an oxide layer with high hardness may be provided on the porous body. It is reported that an electrode using a titanium oxide powder provides a certain level of power generation efficiency (JP-A 2011-154988; Patent Document 1).
In typical solar cells such as silicon-based solar cells, the power generation efficiency depends on the amount of sunlight applied. Therefore, the electricity output rapidly decreases when there is a sudden change in the weather.
To address such a problem, JP-A 2009-135025 (Patent Document 2) proposes providing a solid electricity storage layer on a titanium oxide layer. However, forming a two-layered structure with the solid electricity storage layer by itself has made only a limited contribution to improving the power generation efficiency and the electricity storage capability.